The present invention relates to oxygen supply systems for aircraft. The systems of the present invention may be embodied both as original equipment for new aircraft, and as conversion equipment for converting existing aircraft.
Aircraft operating above certain altitudes require an oxygen supply system for both the passengers and the crew. The oxygen supply system for the passengers is an emergency system, to supply oxygen in the event of a decompression in the airplane cabin while the aircraft is above 14,000 ft. The system for the crew supplies oxygen on a demand basis, continuously or intermittently at the rate required.
Most or all of the oxygen supply systems used in presently operational aircraft are supplied by high pressure oxygen tanks, which have a number of dis-advantages: First, such systems are hazardous, involving both a pneumatic hazard because of the high pressure gas (usually about 1800 p.s.i), and also a fire hazard particularly when refilling the oxygen cylinders; most operators go to great expense to minimize these hazards by employing specially trained personnel and specially designed maintenance, ground-servicing and oxygenrecharging equipment. Further, high pressure oxygen cylinders have some leakage; accordingly, this may require frequent refilling of the cylinders, maintaining large inventories of cylinders for replenishment, relocating the cylinders to different line stations, and periodically testing the cylinders, all of which involve added costs and possibly even departure delays.
Some military aircraft use liquid oxygen sources, but these also involve similar drawbacks.